> If you ask the vast majority of Americans how many centimeters are in a foot, you'll get blank stares. If you ask them how long 30 centimeters are you'll get

> If you ask the vast majority of Americans how many centimeters are in a foot, you'll get blank stares. If you ask them how long 30 centimeters are you'll get blank stares. The conventions of dealing mainly in centimeters and meters when discussing dimensions of human scale items could use fixing. A simple solution is to promulgate the use of the "metric hand" (or just "hand" for short). 1 hand = 1 decimeter = 10 centimeters; about the width of a human hand. The decimeter has the nice property that it's approximately 4 inches, so there are roughly 3 hands in a foot—similar conversion conversion factor as going from feet to yards. Nice! Error accumulates at only 1.6mm (exactly 1.6mm) per hand. (Equestrian sports already has a "hand" unit. Conveniently, it's defined as 4 inches, and its use is pretty much confined to those circles. There's not much need to distinguish between the two, therefore, but if ever a need arises, we can clarify whether we're talking about "metric hands" or "horse hands".)